U.S. patent number 5,022,188 [Application Number 07/372,349] was granted by the patent office on 1991-06-11 for clamping fixture for detachably fixing a tool, in particular a disc.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Erich Borst.
United States Patent |
5,022,188 |
Borst |
June 11, 1991 |
Clamping fixture for detachably fixing a tool, in particular a
disc
Abstract
A clamping fixture for detachably fixing a tool to a driven
spindle and comprising a flange for applying a clamping force to
the tool and axially displaceable relative the driven spindle and
coupled to the driven spindle for transmitting a torque thereto, a
supporting element for securing the flange against axial
displacement relative to the spindle to prevent the flanges from
applying a damping force to the tool, the supporting element
comprising an annular nut member displaceably mounted on the
spindle adjacent an end of the flange which is remote from the
tool, and having a right-hand coarse thread to be screwed onto the
threaded portion with an external coarse thread of the spindle, a
torsion spring for coupling the annular nut member to the flange,
and a locking device for preventing rotation of the annular nut
member upon actuation of the locking device.
Inventors: |
Borst; Erich
(Leinfelden-Echterdingen, DE) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DE)
|
Family
ID: |
6317198 |
Appl.
No.: |
07/372,349 |
Filed: |
June 14, 1989 |
PCT
Filed: |
December 05, 1987 |
PCT No.: |
PCT/DE87/00560 |
371
Date: |
June 14, 1989 |
102(e)
Date: |
June 14, 1989 |
PCT
Pub. No.: |
WO88/04976 |
PCT
Pub. Date: |
July 14, 1988 |
Foreign Application Priority Data
|
|
|
|
|
Dec 24, 1986 [DE] |
|
|
3644441 |
|
Current U.S.
Class: |
451/342;
451/358 |
Current CPC
Class: |
B24B
23/022 (20130101); B24B 45/006 (20130101) |
Current International
Class: |
B24B
23/02 (20060101); B24B 45/00 (20060101); B24B
23/00 (20060101); B24B 045/00 () |
Field of
Search: |
;51/168,29R,26R,17R,17T,17PT ;83/666,698 ;279/1K,1R,8,97 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rachuba; Maurina
Attorney, Agent or Firm: Striker; Michael J.
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims:
1. A clamping fixture for detachably fixing a discs-like tool to a
driven spindle having a threaded portion with an external coarse
thread, said clamping fixture comprising a flange for applying a
clamping force to the tool, said flange being axially displaceable
relative to the driven spindle and coupled with the driven spindle
in a torque transmitting relationship; a supporting element for
supporting said flange and displaceable relative to said spindle to
prevent said flange from applying a clamping force to said tool,
said supporting element comprising an annular nut member
displaceably mounted on the spindle adjacent an end of said flange
which is remote from the tool, and having a coarse thread to be
screwed onto the threaded portion with an external coarse thread of
the spindle; a torsion spring for directly coupling said annular
nut member with said flange and having opposite ends connected to
said annular nut member and said flange, respectively; and a
locking device including a locking member for preventing rotation
of said annular nut member upon actuation of said locking
device.
2. A clamping fixture according to claim 1, wherein a lead angle of
a coarse thread is so selected that it lies in a reliable
self-locking range of the coarse thread.
3. A clamping fixture according to claim 1, further comprising an
axial bearing located between said flange and said annular nut
member.
4. A clamping fixture according to claim 3, wherein said axial
bearing is a ball bearing.
5. A clamping fixture according to claim 1, wherein the spindle has
a collar, said annular nut member comprising a disc portion axially
displaceable and rotatable relative to the spindle, said clamping
fixture comprising an axial bearing for supporting said disc
portion on the collar of the spindle.
6. A clamping fixture according to claim 5, wherein said bearing is
a ball bearing.
7. A clamping fixture according to claim 1, further comprising a
slot-and-key connection for coupling said flange to the
spindle.
8. A clamping fixture according to claim 1, further comprising stop
means for limiting axial displacement of said flange in a direction
away from said annular nut member.
9. A clamping fixture according to claim 8, wherein said stop means
for limiting axial displacement of said flange comprises a snap
ring to be secured to the spindle.
10. A clamping fixture according to claim 1, further comprising
stop means to be secured to the spindle for limiting axial
displacement of said annular nut member relative to the
spindle.
11. A clamping fixture according to claim 10, wherein said stop
means for limiting axial displacement of said annular nut member
relative to the spindle comprises a collar having an end surface
which is opposite to an end surface of said collar facing said
annular nut member and which serves as a stop for a ball bearing
supporting the spindle in a housing of a power hand tool.
12. A clamping fixture according to claim 1, further comprising a
cylindrical protective sleeve extending axially over an area
including at least portions of said flange and said annular nut
member for covering respective portions of said flange and said
annular nut member and an axial intermediate area
threrebetween.
13. A clamping fixture according to claim 12, wherein said
cylindrical protective sleeve is fixed to one of said flange and
said annular nut member and axially overlaps with a clearance a
respective portion of the other of said flange and said annular
flange member.
14. A clamping fixture according to claim 1, further comprising two
sealing rings arranged on an axial side of said annular nut member
which is remote from said flange to form a double labyrinth
thereat.
15. A clamping fixture according to claim 1, wherein said locking
device includes a spring-loaded thrust bolt transversely
displaceable in a power tool housing.
16. A clamping fixture according to claim 15, wherein said thrust
bolt has an inner end carrying said locking member.
17. A clamping fixture according to claim 16, wherein said annular
nut member has a catch opening facing said locking member, said
locking member comprising a finger engaging in a positive-locking
manner said catch opening upon actuation of said locking
device.
18. A clamping fixture according to claim 17, wherein a housing of
a power hand tool has a guide for guiding said finger, said finger
being secured against rotation.
Description
BACKGROUND OF THE INVENTION
The invention starts from a clamping fixture for detachably fixing
a tool, in particular a disc and comprising two flanges for
clamping the tool therebetween and of which one flange is axially
displaceable on the spindle. Clamping fixtures, in particular for
disc-shaped tools are suitable particularly for portable, power
hand tools, and in this respect in particular for grinding
machines. A clamping fixture of this type has been disclosed
(German Patent Specification 3,012,836) in which one flange, which
is arranged on the side of the tool pointing towards the housing of
the power hand tool, is axially movable relative to the spindle and
designed as a driving plate. This rear supporting flange is coupled
to the spindle in such a way as to transmit torque and is axially
supported in an end position on a shoulder of this spindle. The
other flange, which can be screwed onto the end of the spindle,
consists of a nut having a separate clamping element which is
roughly pot-shaped in cross-section and is supported axially
against the flange of the clamping nut via a coil spring. When this
clamping nut is screwed on and tightened, the pot-shaped clamping
element is pressed axially against the tool via the axially
compressed spring, and the tool is thereby tightened against the
flange on the spindle side, the end face of a cylindrical extension
of the clamping nut coming to bear directly on a facing axial side
of the rear flange and, during further tightening of the clamping
nut, this rear flange on the spindle side being tightened together
with the clamping nut, if necessary until the rear flange comes to
bear axially on the shoulder surface of the spindle. In an angle
grinder, the grinding disc is thereby supposed to be mounted with a
defined contact pressure and this contact pressure is supposed to
be ensured. This clamping fixture is also intended to enable a
quick and simple interchange of the grinding disc and at the same
time avoid overloading of the power hand tool, in particular the
angle grinder. This is because, if the torque acting on the
grinding disc is too great, the grinding disc stops, while the rear
flange and also the clamping nut having the clamping member,
perform a relative movement thereto. The effect of the clamping nut
automatically tightening further in operation, makes it
considerably more difficult to loosen the clamping nut when
changing the grinding disc. Therefore loosening of the clamping nut
is here only possible with the assistance of a special auxiliary
tool, the spindle, depending on the design of the machine, having
to be appropriately counterheld by a second auxiliary tool, e.g., a
spanner.
SUMMARY OF THE INVENTION
The object of the invention is to provide a clamping fixture in
which a tool change is possible without any auxiliary tool, which
tool change, in addition, can be performed quickly and safely. The
clamping fixture is shifted from the front area, exposed when used
as specified, into the area between tool and bearing flange of the
housing so that any risk of damage, e.g. chafing on the work piece,
is countered. Furthermore, the clamping fixture is simple and
robust in construction as well as adequately protected against
dirtying from the outside. Any wear of functionally important parts
is taken into account. Simple and easy two-hand operation is
achieved. The front clamping nut is taken over unchanged in a known
manner so that recourse can be made here to standardised,
cost-effective parts. At the same time, it is still possible in
especially stubborn cases, e.g. in the event of a rusted-in
clamping nut, for a spanner to be placed thereon, and the clamping
nut can be released with this auxiliary tool. The supporting flange
is in a rotationally fast positive-locking connection with the
spindle so that relevent regulations are complied with. In
addition, the supporting flange is removably attached, which
further facilitates the tool change.
The novel features which are considered as characteristic for the
invention are set forth in particular in the appended claims. The
invention itself, however, both as to its construction so to its
mode of operation, together with additional objects and advantages
thereof, will be best understood from the following description of
preferred embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a schematic axial longitudinal cross-sectional view of
a first embodiment of a clamping fixture according to the present
invention as part of an angle grinder having a mounted grinding
disc,
FIG. 2 shows a schematic sectional view along line II--II in FIG. 1
of a detail of the clamping fixture,
FIG. 3 shows a schematic axial longitudinal cross-sectional view
roughly corresponding to that in FIG. 1 of a second embodiment of a
clamping fixture according to the present invention,
FIG. 4 shows a developed side view of detail IV in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 schematically shows the lower part of a portable power hand
tool which is designed, for example, as an angle grinder and has a
spindle 10 which is motor-driven via a gearing and is supported in
housing 11 at one end by a needle bearing 12 and, at an axial
distance therefrom, by a ball bearing 13. The inner ring of the
ball bearing 13 is axially supported on a shaft collar 14. At the
end, the spindle 10 is provided with a threaded portion 15 which
has an external thread 16. The spindle 10 serves to drive a tool 17
which consists, for example, of the grinding disc as shown or
another tool disc, e.g. a cup wheel, brush, a rubber plate or the
like. The tool 17 is detachably fixed on the spindle 10 by a
clamping fixture. The clamping fixture has two flanges 18 and 19
between which the tool 17 can be clamped axially in place. One
flange 19 is formed by a clamping nut 20 which has a hub part 21
and a through internal thread 22 with which the clamping nut 20 is
screwed onto the external thread 16. The tool 17, during fixing, is
centred on the outer peripheral surface of the hub part 21.
The other flange 18 forms a mating flange. It is held in an axially
displacable manner on the spindle 10 and in the process is coupled
to the spindle 10 in such a way as to transmit torque. Used for
this purpose is a slot-and-key connection having a Woodruff key 23
which is accommodated in a positive-locking manner in the spindle
10 and engages into an axial through groove 24 of the flange
18.
On the axial side of the flange 18 remote from the tool 17, a
supporting element is arranged on spindle 10 so as to be movable
relative thereto, which supporting element consist of an annular
part 25 and is here designed as a nut 26. The nut 26 is located at
least a slight axial distance from the flange 18. It has an
internal thread 27 with which it is movable on the thread on a
threaded portion 28 of the spindle 10. The external thread of the
threaded portion 28 and the internal thread 27 of the nut 26 are
each designed as right-hand coarse threads whose lead angle is
selected to be of such a size that the coarse in the reliable
self-locking range.
Arranged axially between the flange 18 and the nut 26 is an axial
ball bearing 29 via which the flange 18 is supported axially on the
nut 26.
Placed between the flange 18 and the nut 26 is a torsion spring 30
which acts with one leg end 31 on the flange 18 and with its other
leg end 32 on the nut 26. The nut 26, via the coarse thread of the
threaded portion 28, is pressed against the axial ball bearing 29
by the force of the torsion spring 30. This axial screw force is
transmitted to the flange 18 whose axial displacement in the
direction away from the nut 26 is limited by a stop 33 in the form
of a snap ring on the spindle 10.
An axial movement of the nut 26 relative to the spindle 10 and in
the direction away from the flange 18 is limited by the shaft
collar 14 of the spindle 10.
Fixed to the flange 18 is a cylindrical protection sleeve 34 which
extends axially over at least an area of both the flange 18 and the
nut 26 and as a result protectively covers in this area the flange
18, the nut 26 and axial intermediate area between the two. The
protection sleeve 34 provides the radial support to the outside for
the unrestrained balls of the axial ball bearing 29 and at the same
time seals off to the outside the area between the nut 26 and the
flange 18. The protection sleeve 34 overlaps the nut 26 axially
with clearance for movement so that it does not prevent the
relative movement of the nut 26 relative to the spindle 10 plus
flange 18.
In addition, arranged on axial side of the nut 26 remote from the
flange 18 are two sealing rings 35, 36, of which one 35 is held on
the nut 26 and the other 36 is held on a part of the bearing flange
37 of the housing 11. The two sealing rings 35, 36 together form a
double labyrinth and protect the axial ball bearing 29 and the
coarse thread of the threaded step 28 as well as the internal
thread 27 of the nut 26 from dirt.
A locking device 38 accessible and operable from outside is
allocated to the nut 26. This locking device 38 has a thrust bolt
40 which is loaded by a spring 39, is reset into the inactive
disengagement position and is held and guided in a guide 41 of the
bearing flange 37 so as to be radially displacable in a translatory
manner with regard to the spindle 10. At the end on the inside, the
thrust bolt 40 carries a locking member 42 which, when the locking
device 38 is actuated, can prevent the nut 26 from turning. The
locking member 42 here consists of a roughly strip-like finger 43
angled at the lower end. This finger 43 is secured against tilting
or turning about the axis of the thrust bolt 40 and guided in a
guide 44. The guide 44 is formed, for example, by two adjacent ribs
45, 46 of the housing 11. Recesses 47, 48 adjacent to the ribs 45,
46 ensure that the translatory movement of the finger 43, triggered
by displacement of the thrust bolt 40, is not blocked, for example
by dirt or such like trapped impurities.
On the outside, the nut 26 has at least one, conveniently a
plurality of catch openings 49, 50 which are arranged at equal
circumferential angular distances from one another, are open to the
outside and towards the finger 43 and are adapted to the dimensions
of the finger 43 in such a way that the finger 43 fits into the
catch openings 49, 50 when the thrust bolt 40 is pressed in a
direction of arrow 51 by hand.
If the tool 17 is to be removed and changed, the thrust bolt 40,
when the motor is switched off, is pressed by one hand from the
outside in the direction of arrow 51 up to the stop, and the other
hand takes hold of the tool 17 and rotates the latter together with
the clamping fixture including the flange 18, the spindle 10 and
nut 26 until the finger 43 engages into a catch opening 49 or 50
moving into its area, whereupon the nut 26 is prevented from
turning during this rotation. The thrust bolt 40 is then held by
hand in this engaged position. At the same time, the other hand
exerts a torque on the tool 17 in anti-clockwise direction. This
torque is transmitted by the tool 17 via the flanges 18, 19 to the
spindle 10 and its threaded step 28 having a coarse thread. If the
torque exerted by hand in this manner now becomes greater than the
friction moment in the coarse thread including the torque of the
torsion spring 30, the nut 26 is released from its axial contact
with the axial ball bearing 29 and, during further rotation, is
displaced axially in a direction away from the flange 18 up to the
stop at the shaft collar 14. Consequently, the axial ball bearing
29 and with it the flange 18 become freely movable axially so that
the clamping pressure effective between both flanges 18 and 19 and
clamping the tool 17 in place drops and the clamping nut 20 is
relieved. The latter can now be fully unscrewed from the threaded
step 15 by hand and then the tool 17 can be replaced.
The release moment at the periphery of the tool 17 is dependant
upon the lead angle of the coarse thread on the threaded step 28
and the nut 26. The greater the lead angle, the smaller the release
moment. This lead angle is established in such a way that the
coarse thread of the threaded step 28 and the internal thread 27 of
the nut 26 lie in the reliable self-locking range, and in fact
while allowing for the torque of the torsion spring 30, which
torque counteracts the release moment.
If the tool 17 has been exchanged for another and if this other
tool is to be clamped, the locking device 38 is again actuated by
hand in the manner described above so that the finger 43 engages
into a catch opening 49, 50 of the nut 26. The clamping nut 20 is
screwed down gently with the other hand and thus the new tool 17 is
likewise gently tightened. This is sufficient, since, when the
motor is subsequently switched on, the tool 17 tightens
automatically in operation.
The axial ball bearing 29' arranged between the nut 26 and the
flange 18' has the advantage that the surface friction between the
two is thus reduced to a rolling friction and is thus virtually
negligibly small.
The clamping fixture described has manifold advantages. It lies in
the protected area between the tool 17 and the bearing flange 37
extending thereabove, and the risk of any damage or impairment when
using the power hand tool as specified is completely averted. What
is more, reliable protection against dirt, dust and other
contaminants is obtained by simple means. The clamping fixture is
simple and robust in construction. Any wear of functional parts of
this fixture is reduced to a minimum or even eliminated completely.
The clamping fixture is exceptionally simple, cost-effective and
quick, safe and easy to handle. It enables the tool 17 to be
quickly and safely changed without requiring any additional special
tools for this purpose. Simple and easy two-hand operation is
achieved. In the process, the standardised clamping nut 20 present
in other machines will be retained unchanged, as will a
rotationally fast, positive-locking connection between the flange
18 supporting the tool 17 and the spindle 10. Thus corresponding
relevant regulations are complied with. In addition, it is
advantageous that the flange 18 is mounted undetachably on the
spindle 10. The clamping fixture is not restricted to grinding
discs such as tool 17. On the contrary, other tools, e.g. cup
wheels, brushes, rubber plates or the like can be also be clamped
without auxiliary tool.
Locking devices for the spindles of angle grinders are known per
se. In known power hand tools, however, these locking devices are
located in the gearing space. The design according to the invention
differs therefrom in that the locking device 38 is instead arranged
in the area of the bearing flange 37 and the ball bearing 13. This
shifting of the spindle-locking device has the advantage that
sealing problems do not occur and, furthermore, catch openings
necessary at the crown wheel for the positive locking of the
spindle are dispensed with, as a result of which the crown wheel
comes substantially cheaper and also the configuration of the
housing 11 becomes simpler and more cost-effective. In addition,
the stress on the individual parts of the spindle-locking device is
substantially reduced. During release, the stress is, for example,
only about 6% of that of any other known spindle-locking devices.
The advantage of the lateral arrangement of the thrust bolt 40
accessible from outside is also retained here in the locking device
38 according to the invention. Each time before the tool 17 is
clamped the nut 26 is positively returned into the initial position
via the locking device 38.
In the second embodiment shown in FIGS. 3 and 4, reference numerals
increased by 100 are used for the parts which correspond to the
first embodiment so that reference is thereby made to the
description of the first embodiment to avoid repetitions.
The second embodiment differs from the first embodiment in that the
annular part 125 which serves as supporting element for the flange
118 consists of a disc 152 which is displacable and rotatable
relative to the spindle 110. The spindle 110, instead of being
provided with the threaded portion 28 as in the first embodiment,
is provided in this area with a continuous cylindrical outer
peripheral surface.
The axial ball bearing arranged axially in the first embodiment
between the annular part 25 and a nut 26 is omitted in the second
embodiment. Arranged instead on the axial side of the disc 152
remote from the flange 118 is a schematically indicated axial ball
bearing 153 on which the disc 152, with the facing axial side, is
supported. The axial ball bearing 153 is in turn supported on the
shaft collar 114 of the spindle 110.
The cylindrical protection sleeve 134 is here firmly attached to
the disc 152. It covers an axial part of the flange 118 and does
this with clearance for movement. As in the first embodiment, the
disc 152 and the flange 118 are coupled by the torsion spring
130.
As apparent in particular from FIG. 4, both the disc 152 and the
flange 118, on the end faces axially facing one another, have,
e.g., three sloping surfaces 152a and 118a respectively, which
follow one another at distances in the peripheral direction and are
inclined to the left. The sloping surfaces 152a, 118a are axial
wedge surfaces with which the flange 118 and the disc 152 bear
axially against one another, as follows from the developed view
according to FIG. 4.
In this arrangement, the wedge angle .alpha. of these sloping
surfaces 152a, 118a is selected to be of such a size that it lies
in the reliable self-locking range.
The torsion spring 130, which, as in the first embodiment, is
supported with one leg end 132 on the disc 152 and with its other
leg end 131 on the flange 118, rotates the disc 152 and the flange
118 relative to one another in such a way that both parts slide up
on the sloping surfaces 118a, 152a and are thereby move apart
axially. This axial spreading movement is limited in one direction
by the shaft collar 114 and in the other direction by the stop 133
in the form of the snap ring of the spindle 110.
If the tool 117 is to be removed and changed, first of all, as has
been described for the first embodiment, the disc 152 is
rotationally locked by the locking device 138, which is designed
just as in the first embodiment. If the tool 117 is then rotated
anti-clockwise by the other hand, the flange 118 and the spindle
110 are also driven along in the process. The rotation of the
flange 118 anti-clockwise causes the sloping surfaces 118a of the
flange 118 to slide towards the wedge bottom of the sloping
surfaces 152a of the rotationally locked disc 152, which leads to
corresponding axial relief, whereupon the clamping nut 120 becomes
loose and can easily be unscrewed fully by hand. The sliding
movement of the flange 118 with the sloping surfaces 118a towards
the wedge bottom of the sloping surfaces 152a is limited by locking
surfaces 154 of the disc 152 and 155 of the flange 118, which
locking surfaces 154 adjoin the sloping surfaces and are directed
axially towards one another. These locking surfaces 154, 155 form
dog steps.
As soon as the releasing torque is reduced to zero when the tool 17
is being released, the torsion spring 130 is able to rotate the
flange 118 relative to the disc 152 so that the sloping surfaces
118a of the flange 118 slide towards the wedge top on the sloping
surfaces 152a of the disc 152, as a result of which the two parts
152, 118 are again thrust apart axially. The tool 117 is clamped in
the thrust-apart position.
In another embodiment (not shown) rolling bodies are located
between the sloping surfaces 118a, 152a, as a result of which the
surface friction between the sloping surfaces 118a, 152a is further
reduced.
While the invention has been illustrated and described as embodied
in a clamping fixture for detachably fixing a disc-type tool, it is
not intended to be limited to the details shown, since various
modifications and structural changes may be made without departing
in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic or specific
aspects of this invention.
* * * * *